A workpiece within the meaning of the invention is a body to be machined, having a substantially flat surface for machining. The workpiece can be an elongate body that has a defined cross-sectional geometry. The workpiece within the meaning of the invention can be composed of differing materials, for example plastic or wood, but also, in particular, of steel. Such workpieces are used for differing purposes in all technical fields. To be considered in greater detail here, by way of example, is the application of a workpiece as a rail of a track body.
Workpieces have to be machined as part of their production. Frequently in this case, particular attention is paid to an exact cross-sectional geometry. Moreover, the creation of a flat and/or planar surface is important. It is precisely in the case of a workpiece subjected to mechanical stress—such as a rail of a track body—that the cross-sectional geometry and the surface must be restored regularly.
There are numerous known stock-removing methods of machining by means of a geometrically defined cutter, for example planing and milling, for creating a planar surface of a workpiece. Usually in such cases, the workpiece is moved through and/or past the apparatus for machining the workpiece. For machining of workpieces of indeterminate length, such as rails, the apparatus for machining the workpiece is usually moved along and/or on the stationary workpiece.
Usually, for the purpose of machining such a workpiece, apparatuses are used that have a milling cutter driven in rotation, as described in DE 10 2006 008 093 A1. The milling cutter has a set of cutters for milling a rail head, the cross-sectional geometry of which cutters is composed of approximately circular partial arcs of various radii, each partial arc forming a trace on the running surface of the track rail. The multi-trace milling cutter has a plurality of rectilinear cutter elements, next to one another, which are adapted to the contour of the rail head, and which enable the entire contour to be machined in one operation. The individual cutters can also be disposed in a mutually offset manner on the milling cutter. WO 02/06587 A1 also describes a method for reprofiling at least the travel surface of a rail, preferably of the convex part of the rail-head cross-sectional profile of a rail, in particular of a railway rail, that comprises the travel surface, through circumferential milling with more than five milling traces next to one another in the longitudinal direction of the rail. Further apparatuses for stock-removing remachining, in particular for the milling of rail heads laid in the track, are described in the publications EP 0 952 255 B1, U.S. Pat. No. 4,583,893, U.S. Pat. No. 5,549,505, EP 0 668 398 B1, EP 0 668 397 B1, U.S. Pat. No. 4,275,499, DE 32 22 208 C2, WO 95/20071 A1 and DE 80 34 887 U1. Disadvantageous in the case of milling are the machining traces that occur on the machined surface, for example undulations and/or corrugations.
In contrast thereto, apparatuses are known wherein the rail heads are machined by means of a so-called rail plane. The publication DE 28 41 506 C2 discloses such an apparatus, wherein stock-removing blades machine the rail in a continuous advance motion. Owing to the great removal depth, a rail plane removes irregularities, even on highly corrugated rail portions, with a high working accuracy. By means of planing, planar surfaces can be produced that, compared with milling, have only negligible remaining machining traces. Disadvantageous in the case of planing, particularly compared with the milling methods, are the lesser advance speed, a greater force requirement in the direction of advance, a long chip and/or the frequently longer downtimes.
For this reason, at present it is usual for rails to be machined initially, in a first operation, by means of a milling cutter. Subsequently, in a further operation, the machining traces that occur on the machined surface during milling, such as undulations and/or trace patterns, are then reduced by grinding. Apparatuses for grinding are described in the publications U.S. Pat. No. 4,583,895 A1, DE 32 27 343 A1, DE 28 01 110 A1 and EP 1 918 458 A1.
The publication AT 400 863 B describes an apparatus for the stock-removing remachining of a rail by means of a revolving tool guided along the machining strip, wherein the cutters are held in carriers that constitute links of a link chain guided endlessly around deflection wheels.